This invention relates to upright telescopic supports for work surfaces such as desks, table tops, etc., and more specifically to extruded aluminum telescopic uprights which are extensible and contractible with fluid cylinders.
Aluminum telescopic uprights of certain types are known for use to support work surfaces and the like. A typical such arrangement is depicted in FIG. 1, which is illustrative of prior art and also to explain the present invention, with the prior art upright itself being more specifically depicted in FIGS. 21-23 hereof. The conventional method of extending and contracting these uprights is with fluid cylinders enclosed in the uprights and actuated by hand operated, crank-type or motor driven fluid pumps. A common form of the upright involves a combination of three extruded aluminum members as in FIGS. 21-23. The two outer members 1, 2 snap together and cooperate with a one-piece inner member 3. These are retained in spaced relationship by a pair of U-shaped plastic bearings 4 therebetween. The inner member has a rectangular central portion with tabs, to receive the fluid cylinder bracket assembly.
Difficulties are experienced with these prior units because of the substantially large tolerances which occur when extruding aluminum. Consequently, the fit between the three units can be loose, i.e., sloppy, so that the work surface is loose and wobbly, or the fit can be overly tight so that the unit resists telescopic adjustment. A loose interfit creates significant potential problems with full or near full cylinder extension and relatively high cantilever loads. Further, the snap interfit between the two outer elements can be difficult to make and/or maintain. Also, the prior art does not offer an integral means for mounting a cross beam or stretcher support.